Mars rover Curiosity will phone home on NASA's interplanetary Internet

Now that the Mars Science Laboratory rover, better known as Curiosity, has landed safely in a Martian crater, it can begin its exploration of the surface in search of evidence of life on the Red Planet.

One key to what scientists find out about Mars will be NASA’s Deep Space Network, a kind of interplanetary Internet that will carry the data Curiosity collects the 139 million miles or so (that’s the average distance, but it can vary greatly depending on the planets’ orbits) back to Earth.

The Deep Space Network (DSN), which also carries communications from other space craft within and without the solar system, comprises large dish antenna arrays at three locations approximately 120 degrees apart on Earth: at Goldstone, Calif., in the Mojave Desert; near Madrid, Spain; and near Canberra, Australia.

Each complex has a 70-meter antenna and several 34-meter antennas, sizes that give them strong signals and the ability to send and receive high quantities of information, NASA said. The mission controllers at the Jet Propulsion Laboratory will communicate with Curiosity primarily via the orbiters about 250 miles above Mars, including the Odyssey satellite, the Mars Reconnaissance Orbiter and the European Space Agency’s Mars Express.

Curiosity could send signals directly to Earth via its X-band transmitter, but for only about three hours a day because of power limitations. It can more easily connect with the orbiters using its UHF software-defined radio.

During an eight-minute stretch, the rover can send about 60 megabits of data to the orbiter, which can then relay the information to Earth, NASA said.

Odyssey will have a line of sight to Earth for about 16 hours a day and can operate its radio for longer stretches because it has larger antennae than Curiosity and its solar panels get light most of the time.

The large, 70-meter antenna at Goldstone has been in operation for more than 40 years, although it was upgraded in 2010. It was built when NASA missions began leaving the orbit of the Earth and smaller antennas were unable to track them.

NASA also is working on improving the transmission speeds through space, and working on improving its Ka-band (26 to 40 MHz) availability for 1 gigabit/sec links. The agency also plans on using arrays of smaller antennae, which are less expensive than building more very large models and can, in combination, provide the highest possible data rates.

Arraying would support operating at X-band and Ka-band frequencies at data rates above 100 megabits/sec, according to NASA.

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Kevin McCaney is editor of Defense Systems. Follow him on Twitter: @KevinMcCaney.